In general, a painting apparatus for spraying liquid paints on a work piece is largely constituted by a color change valve device for selecting and supplying paints of plural colors or wash fluids as needed, and a coater unit for spraying the paint supplied through a pipe from the color change valve device.
The color change valve device is structured of a manifold an inside of which forms a paint passage, and to which connector passages are provided to radially penetrate therethrough at plural locations axially spaced from each other, a wash fluid valve provided to be connected to the most upstream side connector passage among the respective connector passages in the manifold for performing supply and blockade of the wash fluid to the paint passage, and plural paint valves provided to be connected to the connector passages in the manifold to be positioned at the downstream side of the wash fluid valve for performing supply and blockade of the paint to the paint passage (Patent Document 1).
The color change valve device selects a desired paint from plural kinds of paints and supplies the selected paint to the coater unit. Accordingly, the color change valve device, at the time of changing a paint to be used for a spray work, washes out the previous color paint used in the previous spray work and stagnating in the paint passage of the manifold or the like, and, after washing out the previous color paint, supplies the next color paint to be used in the next spray work toward the coater unit.
In a case of performing the wash work of the previous color paint stagnant in the paint passage of the manifold or the like, when the spray work using the previous color paint is completed, the paint valve having supplied the previous color paint is closed. Thereafter, the wash fluid valve is opened to supply the wash fluid of wash air, a wash liquid or the like to the paint passage. Therefore, the wash fluid flows from the upstream side to the downstream side in the paint passage to push out the previous color paint stagnant in the paint passage and wash the previous color paint adhering to the inner wall surface of the paint passage.
Here, the previous color paint stagnant in the paint passage flows straight along the paint passage. Then the paint as viscosity fluid generates a pipe pressure loss on the inner wall surface side of the paint passage. Therefore, a velocity of the paint at the time the paint flows through the inner wall surface side (radial outside) in the paint passage is slower than that at the time the paint flows through an axis central part in the paint passage. Due to this phenomenon, the flowing velocity of the wash fluid is made slower at the inner wall surface side in the paint passage, and therefore the previous color paint can not be effectively pushed or flowed out by the wash fluid, creating the cause of degrading the wash performance.
Therefore, there is known a color change valve device which aims at improving the wash performance on the previous color paint stagnant in the paint passage. The color change valve device according to the conventional art provides an air-liquid mixer, which is composed of plural elements formed by twisting a plate body, in the paint passage. By flowing the wash fluid in the paint passage, the air-liquid mixer forms a wash liquid having fine, uniform air bubbles, and the wash liquid washes the previous color paint in the paint passage (Patent Document 2).
On the other hand, there is known the structure of improving the wash performance on the previous color paint stagnant in the paint supply line for supplying the paint from the color change valve device to the coater unit. This conventional art has the structure in which an element formed by twisting a plate body is housed in a joint component positioned at the upstream side of the paint supply line, and the wash fluid is forced to spirally flow in the paint supply line by the element, thus washing the previous color paint having adhered to the inner wall surface of the paint supply line (Patent Document 3).